A railway train consists of a number of carriages releasably secured together by a carriage coupler assembly. That coupler assembly can include a rack or pinion (link and pin-type couplers) retaining the carriages together during motion. Other types include automatic coupling assemblies which resemble a right-handed fist, wherein the jaw of the couplings is opened and when the carriages come together the coupling is locked closed. A lever lifts a locking key in either coupling to uncouple the carriages apart.
As railway trains have become more complicated, with electrical power and controls connecting one carriage to another, systems for coupling those power and control circuits have been needed. Those circuits typically allow remote control of the carriage doors, lighting, security systems and the like.
Existing electrical couplers are usually either cables or conduits with plugs at one end and hard-wired at the other end. The plug end couples to a receptacle on the adjoining carriage. Where existing systems are adopted, it is also necessary to provide a parking or dummy receptacle to hold the jumper when carriages are disconnected. Alternatively, it is possible to use receptacles at each end of the carriages and connect adjoining carriages with a double-plugged jumper.
Electrical railway couplers typically fail because they are used in harsh environments where there are severe vibrations, changes in temperature, acidity and humidity. Water and dirt commonly enter into the electrical contacts causing failure of the electrical circuits. Further, any coupler assembly must not be too heavy, bulky or difficult to fit, otherwise operators will resort to hammers, levers and other tools to force parts together, damaging sensitive componentary. Maintenance is also a significant issue in railway train systems and any assembly must be easy and inexpensive to maintain.
Existing systems based on plugs and receptacles are slow to disconnect and re-connect, particularly at night and during poor weather conditions. If they are left joined when the mechanical coupler between two carriages is released, significant damage can be caused to the electrical system because the cabling is stretched to breaking point as carriages are shunted. Looser jumpers can be lost, while if one end is disconnected and the other end left in place, the jumpers can be dragged along the ballast, smashing the electrical connectors.
Separate plugs and receptacles are bulky and the hanging catenaries of cables are vulnerable to shrapnel damage from flying ballast. Receptacle covers are often left open due to operator error, allowing further encrustation of electrical contacts with dirt, acidic and alkaline washing solutions, and water, snow and ice.